WASHINGTON – The Senate's Republican leader said Sunday he is reserving judgment on whether to support former Sen. Chuck Hagel, the front-runner to be the next defense secretary, and predicted that his former colleague would face serious question about his stands on Iran and Israel.

President Barack Obama, who returned to the White House on Sunday after his vacation in Hawaii, may round out his new national security leadership team this coming week, with a nomination for Pentagon chief expected and a pick to lead the Central Intelligence Agency possible.

A congressional aide said Senate Democrats have been given a heads-up from the White House that Hagel's selection is imminent. The aide was not authorized to discuss the matter publicly and spoke on condition of anonymity.